| MadSci Network: Chemistry |
First a little background:
The body of the average beverage can is made of series 1100 aluminum (essentially pure aluminum) since it is ductile and can be drawn into a very thin walled structure. The lid of the can is made of a series 3000 aluminum with the principal alloying agent being magnesium. This alloy is more brittle than the 1100, so the flip top tears easily.
Aluminum cans are frequently coated with epoxy or other polymer inks or paints on both the inside and the outside to provide some corrosion protection (phosphoric acid is one of the ingredients in a cola drink), as well as to let you know what you are buying. When cans are recycled, the paint is typically burned off prior to remelting the aluminum.
The melting point of the aluminum can could be affected if there were metallic ingredients in the paint which could alloy with the aluminum. In this case, the paint and colorants in the paint are entirely organic, that is, there are no metals in the coating. When the paint burns, the coating turns to water and carbon dioxide. In the process, some of the aluminum also oxidizes which affects how much aluminum can be recovered. So, the bottom line is that the melting point of the can is independent of the amount of coating on the can.
There are a number of interesting sites concerning metal cans. You might try the following as a starting point: http://www.cancentral.com/
Try the links in the MadSci Library for more information on Chemistry.